1. Field of the Invention
The present invention relates to a wire-tensioning device.
More particularly, the invention relates to a device for tensioning corona-discharge wires.
Still more specifically, the invention relates to a device for tensioning corona-discharge wires such as are used in electrostatic copiers.
2. The Prior Art
For reasons known to those skilled in the art it is necessary for corona-discharge wires to be taut, i.e. not to have any slack. This is true particularly, although not exclusively, in electrostatic copying machines.
Devices for this purpose are already known, for example from German allowed application No. 2,641,396. In the device disclosed therein the free end of a corona wire (the other end is secured in suitable manner so as to be fixed) is engaged and the wire at the same time tensioned by means of a wedge which is inserted transversely to the elongation of the wire into a slightly conical opening. However, such an arrangement can transmit only a relatively limited tension to the wire since tensile forces acting in the longitudinal (i.e. tensioning) direction of the wire can in effect occur only at that edge at which the wire end portion entering beneath the wedge is first engaged and clamped by the wedge. This is understandable because, if it were not the first wire end engaged by the wedge which is clamped without freedom of escaping movement, then the tensioned wire would be capable of lifting the wedge out of its seat. There is, therefore, only a single clamping edge or point in this arrangement, and this in turn means that where the material is engaged at this single point the material of the wire can begin to flow under the very strong stresses acting upon it at this point, with the result that the originally achieved degree of tensioning deteriorates over a period of time, and sometimes deteriorates very rapidly.